function merge(l1, l2) {
    let temp = res = new NodeList(0)
    while (l1, l2) {
        if (l1.val > l2.val) {
            temp.next = l1;
            l1 = l1.next
        } else {
            temp.next = l2;
            l2 = l2.next
        }
        temp = temp.next;
    }
    temp.next = l1 ? l1 : l2
    return res.next
}